Suppression of myopathic lamin mutations by muscle-specific activation of AMPK and modulation of downstream signaling

Hum Mol Genet. 2019 Feb 1;28(3):351-371. doi: 10.1093/hmg/ddy332.

Abstract

Laminopathies are diseases caused by dominant mutations in the human LMNA gene encoding A-type lamins. Lamins are intermediate filaments that line the inner nuclear membrane, provide structural support for the nucleus and regulate gene expression. Drosophila melanogaster models of skeletal muscle laminopathies were developed to investigate the pathological defects caused by mutant lamins and identify potential therapeutic targets. Human disease-causing LMNA mutations were modeled in Drosophila Lamin C (LamC) and expressed in indirect flight muscle (IFM). IFM-specific expression of mutant, but not wild-type LamC, caused held-up wings indicative of myofibrillar defects. Analyses of the muscles revealed cytoplasmic aggregates of nuclear envelope (NE) proteins, nuclear and mitochondrial dysmorphology, myofibrillar disorganization and up-regulation of the autophagy cargo receptor p62. We hypothesized that the cytoplasmic aggregates of NE proteins trigger signaling pathways that alter cellular homeostasis, causing muscle dysfunction. In support of this hypothesis, transcriptomics data from human muscle biopsy tissue revealed misregulation of the AMP-activated protein kinase (AMPK)/4E-binding protein 1 (4E-BP1)/autophagy/proteostatic pathways. Ribosomal protein S6K (S6K) messenger RNA (mRNA) levels were increased and AMPKα and mRNAs encoding downstream targets were decreased in muscles expressing mutant LMNA relative controls. The Drosophila laminopathy models were used to determine if altering the levels of these factors modulated muscle pathology. Muscle-specific over-expression of AMPKα and down-stream targets 4E-BP, Forkhead box transcription factors O (Foxo) and Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α), as well as inhibition of S6K, suppressed the held-up wing phenotype, myofibrillar defects and LamC aggregation. These findings provide novel insights on mutant LMNA-based disease mechanisms and identify potential targets for drug therapy.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • AMP-Activated Protein Kinases / metabolism*
  • AMP-Activated Protein Kinases / physiology
  • Animals
  • Cell Nucleus / metabolism
  • Drosophila Proteins / genetics*
  • Drosophila Proteins / metabolism
  • Drosophila Proteins / physiology*
  • Drosophila melanogaster / genetics
  • Drosophila melanogaster / metabolism
  • Humans
  • Intracellular Signaling Peptides and Proteins / metabolism
  • Intracellular Signaling Peptides and Proteins / physiology
  • Lamin Type A / genetics
  • Lamin Type A / metabolism
  • Lamins / genetics*
  • Lamins / physiology*
  • Membrane Proteins / genetics
  • Models, Animal
  • Muscle, Skeletal / physiology
  • Mutation
  • Nuclear Envelope / metabolism
  • Nuclear Envelope / physiology
  • Peptide Initiation Factors / metabolism
  • Peptide Initiation Factors / physiology
  • Phenotype
  • Signal Transduction

Substances

  • Drosophila Proteins
  • Intracellular Signaling Peptides and Proteins
  • LMNA protein, human
  • LamC protein, Drosophila
  • Lamin Type A
  • Lamins
  • Membrane Proteins
  • Peptide Initiation Factors
  • Thor protein, Drosophila
  • lamin C
  • AMP-Activated Protein Kinases